Lymph node micrometastasis in stage I and II rectal cancer

Purpose The aim of this study was to determine the rate of lymph node (LN) micrometastasis in patients with stage I and II rectal cancer. Methods One hundred eighty patients with either stage I or II rectal carcinoma who underwent curative resection between 1995 and 2010 were included. Forty-eight patients received neoadjuvant chemoradiotherapy. Two sections from each LN were stained with hematoxylin and eosin (H&E) and with CK20 by immunohistochemistry (IHC), respectively. Results A total of 2,257 LNs with a median of 12.5 LNs per patient were examined. For IHC staining, CK20-positive neoplastic cells were found in 4 of the 2,257 LNs (0.2%) from 3 of the 180 patients (1.7%), and all corresponding H&E re-stained sections confirmed that these neoplastic cells were present. Three of four neoplastic cells were micrometastasis, and one was macrometastasis. All occult neoplastic cells were found in 3 of the 85 patients (3.5%) with stage II disease. Conclusion We observed a 3.5% rate of occult neoplastic cells in stage II rectal cancer. Interestingly, the results of IHC staining corresponded with those of H&E re-stained sections, suggesting that the examination of H&E stained section by a competent pathologist may replace IHC staining.